The present invention relates generally to methods and materials for treating humans suffering from hemorrhage due to trauma, by administration of bactericidal/permeability-increasing (BPI) protein products.
Acute traumatic hemorrhage, generally requiring immediate surgical intervention, is a major contributor to morbidity and mortality in the U.S. Bickell et al., New Eng. J. Med., 331:1105-1109 (1994), Tran et al., Surgery, 114:21-30 (1993).! In 1982, there were approximately 165,000 deaths in the U.S. due to trauma, with at least two additional cases of permanent disability for each death. About 50% of these traumatic deaths occur immediately, due to direct injury to the central nervous system, heart, or one of the major blood vessels. Additional early deaths, approximately 30%, occur within several hours after injury, usually due to uncontrolled hemorrhage. The remaining 20% of deaths are so-called "late deaths", occurring during days to weeks after injury, due to complications from the traumatic hemorrhage that include infection or multiple organ system failure (MOSF) in about 80% of the cases. Trunkey, Sci. Am., 249:28-35 (1983), Trunkey, New Eng. J. Med., 324:1259-1263 (1991).!
Among those patients who survive the immediate resuscitative and surgical interventions, approximately 10-40% suffer from a variety of morbidities, including, for example, systemic inflammation, wound infections, pneumonia, sepsis, respiratory failure, renal failure, coagulopathy, and pancreatitis. Hemorrhage and transfusion requirements may be specifically linked to increased risk of postoperative infection, respiratory complications, and multiorgan system failure Agarwal et al., Arch. Surg., 128:171-177 (1993), Duke et al., Arch. Surg., 128:1125-1132 (1993), Tran et al., supra!.
The causes of these complications from traumatic hemorrhage are multifactorial and interrelated. Many morbidities may be related to systemic inflammation following injury. It has also been hypothesized that physical trauma to tissue, direct tissue hypoperfusion, and translocation of endogenous bacteria and absorption of endotoxin from the gut lumen (due to hypoperfusion and/or other injury to the gastrointestinal tract) may play a role in the pathogenesis of these complications. The relevance of these proposed factors in the pathophysiology of the morbidities and late deaths associated with acute hemorrhagic shock in humans, however, is not clear.
Although acute traumatic hemorrhage is one potential cause of hypovolemic shock (i.e., shock due to decreased intravascular volume), there are numerous other potential causes, such as internal bleeding, e.g., gastrointestinal hemorrhage, intraperitoneal or retroperitoneal hemorrhage, hemorrhage into the femoral compartment, intrathoracic hemorrhage, aortic dissection and ruptured aortic aneurysm; excessive fluid loss due to, e.g., severe vomiting due to an intestinal or pyloric obstruction, severe diarrhea, sweating, dehydration, excessive urination (due to diabetes mellitus, diabetes insipidus, excessive diuretics, or the diuretic phase of acute renal failure), peritonitis, pancreatitis, planchnic ischemia, gangrene, burns; vasodilation due to, e.g., nervous system damage, anesthesia, ganglionic and adrenergic blockers, barbiturate overdose, poisons; and metabolic, toxic, or humoral vasodilatation, such as acute adrenal insufficiency, or an anaphylactic reaction. Other causes of shock unrelated to circulatory volume loss include cardiogenic shock (e.g., acute myocardial infarction, cardiac tamponade) and obstructive shock (e.g., acute pulmonary embolism). See, e.g., Manual of Medical Therapeutics, 28th ed., Ewald et al., eds., Little, Brown and Company, Boston (1995); Cecil's Textbook of Medicine, 17th ed., Wyngaarden et al., eds., W.B. Saunders Co., Philadelphia (1985).!
As outlined below in Table I below, a normal individual can rapidly lose up to 20 percent of the blood volume without any signs or symptoms. Limited signs of cardiovascular distress appear with losses up to 30 percent of the blood volume, but signs and symptoms of hypovolemic shock generally appear when the blood loss exceeds 30 to 40 percent of the blood volume.
TABLE I ______________________________________ Percentage Amount of Blood Lost Volume Lost (ml) Clinical Manifestations ______________________________________ 10-20% 500- Usually none, perhaps mild postural hypotension 1000 and tachycardia in response to exercise; vasovagal syncope may occur in 5% of cases 20-30% 1000- Few changes supine; light-headedness and 1500 hypotension commonly occur when upright; marked tachycardia in response to exertion 30-40% 1500- Blood pressure, cardiac output, central venous 2000 pressure, and urine volume are reduced even when supine; thirst, shortness of breath, clammy skin, sweating, clouding of consciousness and rapid, thready pulse may be noted 40-50% 2000- Severe shock, often resulting in death 2500 ______________________________________
The patient is frequently oliguric, with a urinary output of less than 20 mL per hour. Frequently, the physical findings follow a progressive pattern as shock evolves from the early compensated phase to the advanced stages. In Stage I, physiologic compensatory mechanisms, such as increased cardiac output or elevated systemic vascular resistance, are effective and minimal clinical symptoms and signs are observed. In Stage II, these mechanisms cannot effectively compensate for the blood volume loss, and the patient may exhibit hypotension, tachycardia, and hyperventilation. The decreased perfusion of vital organs can result in an altered mental state ranging from agitation to stupor to coma, reduced urinary output, and myocardial ischemia (in patients with coronary artery disease). The external appearance of the patient also reflects excessive sympathetic discharge, with cyanosis, coldness, and clamminess of the skin. In Stage III, which may be irreversible, the excessive and prolonged reduction of tissue perfusion leads to significant alterations in cellular membrane function, aggregation of blood corpuscles, and "sludging" in the capillaries. The vasoconstriction which has taken place in the less vital organs in order to maintain blood pressure in now excessive and has reduced flow to such an extent that cellular damage occurs.
Following traumatic hemorrhage, conventional therapy is directed at stopping the hemorrhage, combating shock, and restoring the blood volume. Prompt fluid resuscitation is preferably given through large-bore catheters placed in large peripheral veins. The pneumatic antishock garment, with sequential inflation of legs and abdominal compartments to 15-40 mm Hg, may temporally stabilize patients by increasing peripheral systemic vascular resistance. Restoration of the blood volume may be achieved by intravenous infusion of electrolyte solutions; colloid solutions of plasma protein, albumin, or dextran; or fresh whole blood. In the emergency situation, electrolyte solutions, albumin, or dextran are preferred over fresh whole blood because of the large amounts of fluid required, the possible delay in transfusion if typing and cross-matching are performed, and the possibility of allergic transfusion reactions. When shock is due to hemorrhage, packed red blood cells should be given as soon as feasible. When hemorrhage is massive, type-specific unmatched blood can be given safely. Rarely, type O blood may be needed.
Rapid infusion of Ringer's lactated or normal saline solution is the most widely used fluid therapy following hemorrhage. An initial infusion of two to three times the volume of the estimated blood loss is administered. Because these solutions are rapidly distributed throughout the intravascular and extravascular compartments, they must be supplemented with colloid solutions. When large volumes of electrolyte solutions are infused, patients often develop peripheral edema and elderly patients may develop pulmonary edema.
The colloidal preparations in wide use include a 6 percent solution of high molecular weight dextran (dextran 70), a 10 percent solution of low molecular weight dextran (dextran 40), and a 5 percent solution of albumin in normal saline. Infusions of dextran 70 produce an initial volume effect slightly greater than the amount infused. Dextran 70 is slowly cleared over one to two days, allowing time for normal physiologic mechanisms to replace the volume lost. Dextran 40 has the advantage of an initial volume effect of nearly twice the amount infused. The lower molecular weight material is more rapidly cleared, however, and the volume-expanding effect is dissipated by 24 hours, before normal volume replacement mechanisms are maximal. Acute renal failure has occurred in a few patients receiving dextran 40. With either dextran solution, volumes in excess of one liter may interfere with platelet adhesiveness and the normal coagulation cascade. A solution of 5 percent albumin in normal saline has the advantage of producing a known volume effect in the hypovolemic patient, but this preparation is relatively costly and time-consuming to prepare. A hypertonic albumin preparation containing 120 mEq of sodium lactate, 120 mEq of sodium chloride, and 12.5 grams of albumin per liter provides a predictable volume effect and minimizes interstitial fluid leakage. Use of hypertonic solutions requires careful monitoring of arterial and central venous pressures to avoid fluid overload. Coexisting problems such as congestive heart failure, valvular heart disease, myocardial ischemia, or renal insufficiency must be carefully monitored, and invasive hemodynamic monitoring must be considered during acute management. Associated coagulopathy and electrolyte imbalance must also be corrected.
BPI is a protein isolated from the granules of mammalian polymorphonuclear leukocytes (PMNs or neutrophils), which are blood cells essential in the defense against invading microorganisms. Human BPI protein has been isolated from PMNs by acid extraction combined with either ion exchange chromatography Elsbach, J. Biol. Chem., 254:11000 (1979)! or E. coli affinity chromatography Weiss, et al., Blood, 69:652 (1987)!. BPI obtained in such a manner is referred to herein as natural BPI and has been shown to have potent bactericidal activity against a broad spectrum of gram-negative bacteria. The molecular weight of human BPI is approximately 55,000 daltons (55 kD). The amino acid sequence of the entire human BPI protein and the nucleic acid sequence of DNA encoding the protein have been reported in FIG. 1 of Gray et al., J. Biol. Chem., 264:9505 (1989), incorporated herein by reference. The Gray et al. amino acid sequence is set out in SEQ ID NO: 1 hereto. U.S. Pat. No. 5,198,541 discloses recombinant genes encoding and methods for expression of BPI proteins, including BPI holoprotein and fragments of BPI.
BPI is a strongly cationic protein. The N-terminal half of BPI accounts for the high net positive charge; the C-terminal half of the molecule has a net charge of -3. Elsbach and Weiss (1981), supra.! A proteolytic N-terminal fragment of BPI having a molecular weight of about 25 kD possesses essentially all the anti-bacterial efficacy of the naturally-derived 55 kD human BPI holoprotein. Ooi et al., J. Bio. Chem., 262: 14891-14894 (1987)!. In contrast to the N-terminal portion, the C-terminal region of the isolated human BPI protein displays only slightly detectable anti-bacterial activity against gram-negative organisms. Ooi et al., J. Exp. Med., 174:649 (1991).! An N-terminal BPI fragment of approximately 23 kD, referred to as "rBPI.sub.23," has been produced by recombinant means and also retains anti-bacterial activity against gram-negative organisms. Gazzano-Santoro et al., Infect. Immun. 60:4754-4761 (1992).
The bactericidal effect of BPI has been reported to be highly specific to gram-negative species, e.g., in Elsbach and Weiss, Inflammation: Basic Principles and Clinical Correlates, eds. Gallin et al., Chapter 30, Raven Press, Ltd. (1992). The precise mechanism by which BPI kills gram-negative bacteria is not yet completely elucidated, but it is believed that BPI must first bind to the surface of the bacteria through electrostatic and hydrophobic interactions between the cationic BPI protein and negatively charged sites on LPS. In susceptible gram-negative bacteria, BPI binding is thought to disrupt LPS structure, leading to activation of bacterial enzymes that degrade phospholipids and peptidoglycans, altering the permeability of the cell's outer membrane, and initiating events that ultimately lead to cell death. Elsbach and Weiss (1992), supra!. LPS has been referred to as "endotoxin" because of the potent inflammatory response that it stimulates, i.e., the release of mediators by host inflammatory cells which may ultimately result in irreversible endotoxic shock. BPI binds to lipid A, reported to be the most toxic and most biologically active component of LPS.
BPI protein has never been used previously for the treatment of humans suffering from hemorrhage due to trauma or the shock associated with traumatic blood loss (i.e., hypovolemic shock). Bahrami et al., presentation at Vienna International Endotoxin Society Meeting, August, 1992, report the administration of BPI protein to rats subjected to hemorrhage. Yao et al., Ann. Surg., 221:398-405 (1995), report the administration of rBPI.sub.21 (described infra) to rats subjected to prolonged hemorrhagic insult for 180 minutes followed by resuscitation. U.S. Pat. Nos. 5,171,739, 5,089,724 and 5,234,912 report the use of BPI in various in vitro and in vivo animal model studies asserted to be correlated to methods of treating endotoxin-related diseases, including endotoxin-related shock. In co-owned, co-pending U.S. application Ser. Nos. 08/378,228, filed Jan. 24, 1995, 08/291,112, filed Aug. 16, 1994, and 08/188,221, filed Jan. 24, 1994, incorporated herein by reference, the administration of BPI protein product to humans with endotoxin in circulation was described. See also, von der Mohlen et al., J. Infect. Dis. 172:144-151 (1995); von der Mohlen et al., Blood 85:3437-3443 (1995); de Winter et al., J. Inflam. 45:193-206 (1995)!. In co-owned, co-pending U.S. application Ser. No. 08/644,287 filed May 10, 1995, the administration of BPI protein product to humans suffering from severe meningococcemia was described.
In spite of treatment with antibiotics and state-of-the-art medical intensive care therapy, human mortality and morbidities associated with hemorrhage due to trauma remain significant and unresolved by current therapies. New therapeutic methods are needed that could reduce or ameliorate the adverse events and improve the clinical outcome of such patients.